When an eye tracker (this is provided, for example, above or below a display screen) is a high-end model, it is possible to presume that a user in front of the display screen reads displayed sentences along them or gives a sentence area a once-over based on measured eye gaze data (i.e. data of the line of sight).
On the other hand, when a low-end eye tracker is used, an error included in the measured eye gaze data tends to become larger than that of the high-end model. For example, even when one eye position on a typical display screen of a personal computer is detected, a true eye position is located inside of an area that includes the one eye position and is about ⅙ of the display screen.
In such a case, even when the user reads a document along the sentences, it is not expected that coordinates of the eye position obtained from the measured eye gaze data are included in the sentence area. Moreover, it is difficult to accurately determine, according to the arrangement of the measured eye gaze data in time series, whether or not transition of eye gaze directions of a certain user is identical with transition of eye gaze directions of another user.
For example, if partial missing of a task to check a document or skip of reading of important portions is detected in a case where people check contents in the same document (for example, checking whether all required fields in a document are filled in or not, or whether all important points are read in a online educational document or not), it is possible to output an alarm to corresponding users. However, the low-end eye tracker cannot detect the aforementioned reading activities with high accuracy.
There is a technique to determine, based on the eye position data and transition speed of the eye position, whether an electronic document displayed on a display unit has been read or not. However, because the technique to determine whether a person read or not depends on the eye position, it is presupposed that the accuracy of the eye tracker is high.
Moreover, although there is a technique that presupposes that the eye tracker is the low-end model, it is determined based on the transition speed of the eye position and curvature obtained from temporal change of the eye positions, whether the user watches a certain area with his or her attention or not. In such a technique, there is no consideration to estimate the relationship between reading activity tendency the user of and that of other users.
Patent Document 1: Japanese Laid-open Patent Publication No. 2013-25656
Patent Document 2: Japanese Laid-open Patent Publication No. 05-56925
In other words, in conventional arts, there is no technique to enable to detect a user that does not perform typical movement of the eye gaze on a display screen, even when the eye tracker having low accuracy is used.